The bright blue color of a blue jay’s feathers makes them easy to spot in the forests where they live, but did you know their feathers aren’t really blue? The blue color is actually just an optical illusion.
The feathers contain a pigment called melanin, which is brown. It appears blue to us because of light scattering, which is kind of like how a prism works. The birds’ wings contain tiny pocket of air and keratin. When light hits the pockets, all the colors of the wavelength are absorbed except blue. Instead, the blue light is refracted, which allows us to see the feathers as blue.
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It’s not just blue jays that play this trick of the eye. It’s true of other blue songbirds as well, including bluebirds and indigo buntings. And the same phenomenon that makes these birds look blue is what makes the sky look blue.